Desirable characteristics of covers for loose leaf papers are an ability to hinge or bend continuously at the spine without breaking and to accept normal printing inks for printing of titles and cover illustrations thereon.
There are many inexpensive materials available which will allow excellent printing of titles and cover illustrations and will be ideally suited for flat covers. However many of these cannot be used as covers as they do not have the ability to be continuously flexed or bent in one place without breaking. This is particularly true of paper- and paper-based products which are conventionally used as covers for paper binders.
The flexible outer covers that are available at present are normally made from expensive materials or the products of special combinations obtained from welding or adhesively securing polyvinylchloride and paper together. These materials usually require special printing processes such as silkscreening to have information displayed thereon. They are expensive.
To the applicant's knowledge there is no device available to act as an independent cover hinge to which various inexpensive flat materials can be attached to form ideal outer covers.
Binders for holding papers are well known and have been made to varying degrees of sophistication. In the simplest form the papers forming the contents of the binder are bound flat against the inside of the back cover and tied down with a flat metal or similar strip. The use of this type of binder makes it difficult to fold the pages for reading.
In ring binders the metal rings are fixed to the spine but the wear and tear of the contents is high. The punched holes in the paper cannot stand up to the rigours of the continuous pulling and jerking while turning the pages individually over the metal, or similar ring. Also the edges of all the pages must follow the shape of the ring in the closed binder.